In my opinion carts at 3 gun matches encorouge poor gun handling and muzzle control .
At the Ft Benning match last year every single shooter that used a cart covered someone with the muzzle of their long guns more than once when loading and unloading them from the carts.
We got pictures the 2nd day to prove it .
If you have so much stuff that you need a cart you probably have too much crap and need to down load . Everything I need to shoot a typical 3 gun match fits into 2 rifle cases and a Green Mountain large range bag .
As for safety.. just because you have a BABY STROLLER does not mean you get to store your long-guns so they're pointing at people, or ACTIVELY SWEEP OTHERS with your long guns.
I got tired of scanning the gaggles of highly-qualified STROLLER PILOTS to get photos of blatant safety violations (which meant - if you think about it - being "downrange" of them).